Modifying the AM PG71 Gearmotor?

[Abrakadabra]

So we’re really liking the PG71 Gearmotor found in the 2012 KOP (am-0914) (i.e. the “AndyGlobe”), but we’re looking for a little more oommph, so we’re thinking about replacing the stock RS-775 series motor with the AM 9015 (am-0912), a higher-powered(?) member of the “RS-500 series”. (Basically, we want to build the am-2084)

1. I am correct that the AM 9015 has more power than the stock RS-775, right?

2. What do I need to use to replace the stock motor? I ordered the spacer (am-2062) and the pinion (am-2068) and I even sourced the M4x55 SHC screws that the spacer drawing says to use. But I believe the RS-550 series motors use M3 screws for mounting. Do I also need some of those, and if so, what length? I don’t have the gearbox available to check for myself - it’s in the bag. We’re planning to do this on Thursday morning in Hartford, so I want to make sure we have everything we’ll need.

Sorry for such a vendor specific question - I would have emailed AM directly, but since these are KOP items, I figured other people might benefit from the answer as well.

Thanks in advance!

[Nate_Laverdure]

I’d be happy to help you figure out how to make this modification, but you should know that once you do it, the motor won’t be legal for use on a 2012 FRC robot.

Note that for the Window motors and the AndyMark gearmotor, the gearboxes are considered integral to the motor, thus the motor may not be used without the gearbox.

EDIT: Er… nevermind. I guess you intend to reuse the original gearbox and toss the (now) unattached original motor. Should be OK then.

[Kevin_Sevcik]

You’d think it’s legal, but the GDC had a fun related answer last year. They declared that you couldn’t remove the gearbox from a first legal window motor and adapt another FRC legal motor to it, because the gearbox was integral to the window lift motor and couldn’t be modified. By that reasoning, pulling the stock motor off a PG71 and replacing it with a different FRC motor would also be illegal. But if you bought the standalone gearbox, it presumably would then be legal.

[Nate_Laverdure]

Unfortunately the STEP files for these items lack internal details that might show how the 500-series motor attaches to the back of the PG71 gearbox.

The spec sheets, dimensional drawings, and product pages (alliteration not intended) are also devoid of the kind of assembly information you’re looking for with the following exceptions:
– The RS-550 does indeed require two M3 mounting screws on a 25mm bolt circle. The RS-775 has M4 screws on a 29mm circle.
– You can tell from the picture that the spacer (am-2062) is made to fit between the main cylindrical gearbox housing and the plate that the motor mounts to. This would suggest that longer-than-normal M3 screws are needed to mount the 500-series motor.

[Abrakadabra]

You’d think it’s legal, but the GDC had a fun related answer last year. They declared that you couldn’t remove the gearbox from a first legal window motor and adapt another FRC legal motor to it, because the gearbox was integral to the window lift motor and couldn’t be modified. By that reasoning, pulling the stock motor off a PG71 and replacing it with a different FRC motor would also be illegal. But if you bought the standalone gearbox, it presumably would then be legal.

You can’t be serious? Why do I feel like I’ve just stepped into a Kafka novel? Has no one else on another team done this? Or are they just not talking about it?

I understand the reasoning last year with the window motor, because that gearbox is not sold separately from the motor. However, under the listing for the PG71 gearbox on the AM website, they specifically say “This is the gearbox that comes with the PG71 Gearmotor.” and "Alternatively, it can be attached it (sic) to the new 9015 motor (am-0912)… ". So, when I take apart the Gearmotor, I have the exact same gearbox, but in order to use it as the vendor intends for it to be used, I have to pay $60 to buy another one?!? (And people wonder why it is so expensive to run an FRC team…)

(Is that really why there is a different sticker on the Gearmotor and the Gearbox? :rolleyes:)

[Nate_Laverdure]

Why do I feel like I’ve just stepped into a Kafka novel?

The antennae, maybe?

This 2012 Q&A entry, about using an “integral” gearbox with a different motor than the one that was originally fitted to it, seems to be applicable:

Q. We want to use a worm-gear for a BaneBot RS550, but we are low on budget and time. the gearbox of a window motor is what we need. says that the window motor is not to be used without its gearbox, but can the gearbox be used without the motor? after all, it is just another 80:1 worm-gear.
A. Yes.

[Abrakadabra]

Nate -
Thanks for digging that out and for trying to help. It seems that this year’s GDC has seen the light (so to speak) compared to last year.

So now back to the original question…has anyone actually done it?

[its_da_PAT]

We did it, and we got the idea for 1114. We turned down the outer cylinder, for weight. Then put the right sun gear on. But you can actually buy them with motor attached now. here.

[nitneylion452]

We did it, and we got the idea for 1114. We turned down the outer cylinder, for weight. Then put the right sun gear on. But you can actually buy them with motor attached now. here.

The OP links to that product, I think what he wants is for it to be cheaper. They may not have room in their budget to buy a new motor, so they want to use 2 things that came in the KOP to make it.

EDIT:
The PG71 with am-9015 spins at an impressive XX RPM with an outstanding XX lb-ft of torque:D

[DriftVelocity]

Spacer for PG Series Gearboxes

This part links the PG71 gearbox to 500 series motors, such as the 9015 motor.

EDIT: somewhat irrelevant, but has anybody else noticed that the 9015 is made by Chiaphua Components Limited (CCL), the parent company of CCL Industrial Motors (CIM)

EDIT 2: no, that is not a coincidence, that is the same company that makes FRC’s staple drive motors.